There is only 1 free gate in Denver. And it's on Concourse A.
I also believe that this 1 gate on Concourse A doesn't have a jetway and is a jetway will be installed when needed. Now is needed obviously, but I guess they want to expand Concourse A at the same time for Frontier mainly and other carriers.
That's true, Concourse B is never empty. At least in my experience.
"Generosity is giving more than you can, and pride is taking less than you need." - Khalil Gibran